Final report for the Richmond Valley Flood Study 2023 - consists of 2 volumes - Volume 1 final report and Volume 2 design flood mapping

Volume 1- Final report; Volume 2- Mapping.

Wallarah Creek Catchment FS - Hydrology data including: * Calibration * Climate Change * Sensitivity Analysis * Design Rainfall

26 maps/figures

Volume 1 - Final Report Volume 2 - Design Flood Mapping

The basis for these features is U.S. Geological Survey Scientific Investigation Report 2017-5024 Flood Inundation Mapping Data for Johnson Creek near Sycamore, Oregon. The domain of the HEC-RAS hydraulic model is a 12.9 mile reach of Johnson Creek from just upstream of SE 174th Avenue in Portland, Oregon to its confluence with the Willamette River. Some of the hydraulics used in the model were taken from Federal Emergency Management Agency, 2010, Flood Insurance Study, City of Portland, Oregon, Multnomah, Clackamas and Washington Counties, Volume 1 of 3, November 26, 2010. The Digital Elevation Model (DEM) utilized for the project was developed from LiDAR data flown in 2015 and provided by the Oregon Department of Geology and Mineral Industries. Bridge decks are generally removed from DEMs as standard practice. Therefore, these features may be shown as inundated when they are not. Judgement should be used when estimating the usefulness of a bridge during flood flow. Comparing the bridge to the surrounding ground can be more informative in this respect than simply looking at the bridge itself. Two model plans were used in the creation of the flood layers. The first is a stable model plan using unsteady flow in which the maximum streamflow is held in place for a long period of time (a number of days) in order to replicate a steady model using an unsteady plan. The stable model plan produced the areas of uncertainty contained in the sycor_breach.shp shapefile. The second is an unstable model plan that uses unsteady flow in which the full hydrograph (rising and falling limb) is represented based on the hydrograph shape of the December 2015 peak annual flood. The unstable model plan produced the flood extent polygons contained in the sycor.shp shapefile and the depth rasters and represents the best estimate of flood inundation for the given streamflow at U.S. Geological Survey streamgage 14211500.

The basis for these features is U.S. Geological Survey Scientific Investigation Report 2017-5024 Flood Inundation Mapping Data for Johnson Creek near Sycamore, Oregon. The domain of the HEC-RAS hydraulic model is a 12.9 mile reach of Johnson Creek from just upstream of SE 174th Avenue in Portland, Oregon to its confluence with the Willamette River. Some of the hydraulics used in the model were taken from Federal Emergency Management Agency, 2010, Flood Insurance Study, City of Portland, Oregon, Multnomah, Clackamas and Washington Counties, Volume 1 of 3, November 26, 2010. The Digital Elevation Model (DEM) utilized for the project was developed from LiDAR data flown in 2015 and provided by the Oregon Department of Geology and Mineral Industries. Bridge decks are generally removed from DEMs as standard practice. Therefore, these features may be shown as inundated when they are not. Judgement should be used when estimating the usefulness of a bridge during flood flow. Comparing the bridge to the surrounding ground can be more informative in this respect than simply looking at the bridge itself. Two model plans were used in the creation of the flood layers. The first is a stable model plan using unsteady flow in which the maximum streamflow is held in place for a long period of time (a number of days) in order to replicate a steady model using an unsteady plan. The stable model plan produced the areas of uncertainty contained in the sycor_breach.shp shapefile. The second is an unstable model plan that uses unsteady flow in which the full hydrograph (rising and falling limb) is represented based on the hydrograph shape of the December 2015 peak annual flood. The unstable model plan produced the flood extent polygons contained in the sycor.shp shapefile and the depth rasters and represents the best estimate of flood inundation for the given streamflow at U.S. Geological Survey streamgage 14211500.

A series of 11 digital flood-inundation maps were developed for a 5.5 mile reach of the lower Pawcatuck River in Westerly, Rhode Island and Stonington and North Stonington, Connecticut by the U.S. Geological Survey in cooperation with the Town of Westerly, Rhode Island and the Rhode Island Office of Housing and Community Development. The coverage of the maps extends from downstream from the Ashaway River inflow at the Westerly, Rhode Island and North Stonington, Connecticut State border to about 500 feet (ft) downstream of the U.S. Route 1/Broad Street bridge on the state border between Westerly, Rhode Island and Stonington, Connecticut. A hydraulic model was used to compute water-surface profiles for 11 flood stages at 1-ft intervals referenced to the U.S. Geological Survey Pawcatuck River at Westerly, Rhode Island streamgage (01118500) and ranging from 6.0 feet (3.32 ft, North American Vertical Datum of 1988), which is the National Weather Service Advance Hydrologic Prediction Service flood category "action stage", to 16.0 ft (13.21 ft, North American Vertical Datum of 1988), which is the maximum rated stage at the streamgage and exceeds the National Weather Service Advance Hydrologic Prediction Service flood category "major flood stage" of 11.0 ft. The hydraulic model reflects the removal of the White Rock dam during 2015-16. The hydraulic model was calibrated using the stage-discharge relation at the streamgage, and documented high-water marks from the March 30, 2010 flood, which had a peak flow slightly greater than the estimated 0.2-percent annual exceedance probability flood flow. The simulated water-surface profiles were combined with a Geographic Information System digital elevation model derived from light detection and ranging (lidar) data with a 1.0-ft vertical accuracy to create flood-inundation maps. The flood-inundation maps depict estimates of the areal extent and depth of flooding corresponding to selected 11 flood stages at the U.S. Geological Survey Pawcatuck River at Westerly, Rhode Island streamgage (01118500).

Complete report + figures

Digital flood-inundation maps for a 6.5-mile reach of the Salamonie River at Portland, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Salamonie River at Portland, Indiana (station 03324200). Near-real-time stages at this streamgage may be obtained from the USGS National Water Information System web interface at https://doi.org/10.5066/F7P55KJN or the National Weather Service Advanced Hydrologic Prediction Service (site PORI3) at https:/water.weather.gov/ahps/. Flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated using the current stage-discharge relation at the Salamonie River at Portland, Indiana, streamgage. The hydraulic model then was used to compute nine water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum and ranging from 10.7 ft or near bankfull to 18.7 ft, which equals the highest point on the streamgage rating curve. The simulated water-surface profiles then were combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.49-ft root mean square error and 4.9-ft horizontal resolution, resampled to a 10-ft grid) to delineate the area flooded at each stage. The availability of these maps, along with information regarding current stage from the USGS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, and for postflood recovery efforts.